All I'm doing is encoding speech output from flite, so the lack of sound quality isn't a huge issue.

That's an understatement! I've been bugging Cepstral to do an ARM/Linux version, but it's not likely to happen. The lack of a reasonable sounding TTS engine is one of the few minuses to the plug. I'm just screwing around with a hobby application, for a real product Cepstral would be happy to do an OEM version. Sigh...

I'm perfectly happy with flite, from the Festival team, though as I said, my needs are very limited. It runs great on the plug, and it will attempt to say anything you throw at it. Sure, it makes a mess of a few things, but it's designed for small systems.